1. Field of the Invention
This invention relates to an interchangeable lens barrel for a photographic camera or a like optical apparatus.
2. Description of the Prior Art
During recent years, there have been proposed electromagnetic diaphragm aperture control devices of the type using electromagnetic energy for electrically controlling the diaphragm device of a lens barrel. There have been also provided diaphragm devices of the type using a stepping motor or a linear motor for controlling the aperture thereof with the driving force of the motor. These electric diaphragm devices are arranged to open and control the diaphragm aperture with an electromagnetic device or a motor by supplying a lens barrel with either a digital electrical signal or an analog electrical signal from a camera body. Conversely, in another type of the conventional electric diaphragm devices, an exposure control mechanism provided within the camera body is controlled with a digital or analog electrical signal by supplying the signal from a diaphragm device disposed within the lens barrel to the inside of the camera body.
The position of the above stated electrical signal sending and receiving means, such as an electrical contact of a lens barrel which is arranged to send and receive electrical signals, is inevitably limited by the arrangement required for attaching and detaching the lens barrel to and from the camera body, and also by the arrangement required for a glass optical system. This limitation has compelled the electrical signal sending and receiving means to be disposed either at a lens barrel mounting arrangement or in the vicinity thereof. Such being the position of the electrical contacts which are disposed on the side of the lens barrel, the electrical contacts tend to become insufficiently electrically connected with corresponding electrical contacts disposed on the side of the camera body, either because of oxidation due to dust or moisture in the air or because of grease on the finger of the operator. It is thus quite possible that the camera will malfunction because of insufficient contact by the electrical contacts. The same problem also exists in an intermediate tube or an extension inserted in between the camera body and the lens barrel, and also in other accessories to be mounted and operated on the camera.